The invention relates to a syringe for introducing an article, such as, in particular, a vascular prosthesis, into the body of a recipient.
In the medical field, the use of syringes is of course widespread, these syringes comprising, as is known per se, a syringe element forming a cylinder for a plunger rod intended to move in this element so as to push the article which is contained therein in such a way as to introduce it at the appropriate site in the body of the recipient patient.
Such syringes are used in particular for the positioning of blood filters designed so as to be permeable to the flow of blood, while at the same time stopping clots capable of migrating towards the heart, in order to prevent, in particular, the risks of embolism.
The best known filters of this type are often in the form of a small truncated basket comprising a series of filiform legs. Examples of these can be found, in particular, in the Patent Applications FR-A-2 570 288 and FR-A-2 573 646, as well as in American Patent U.S. Pat. No. 3,952,747.
Such filters can be positioned via the jugular route or via the femoral route. However, in both cases, the filter must always be arranged with the same orientation in the receiving vein, as is illustrated in FIG. 1 where reference number 1 designates such a blood filter. The latter is in the form of a sort of basket having an essentially ogival head 3 from which there extend arms or legs 5 which are generally expandable and which are provided, if appropriate, with hooks 6 for anchoring to the wall of the vern. The legs 5 open outwards in such a way as to bear, via their free end 5a, against the wall of the vein 7 inside which the filter is essentially centered by being oriented in such a way that the blood flow (the direction of which has been shown diagrammatically by the arrow 9) first comes into contact with the legs and then the narrower joining head 3.
Also in this FIG. 1, the arrows 11 and 13 show, respectively, the direction of positioning of the filter via the femoral route (arrow 11) and via the jugular route (reference 13). It will be understood from this illustration that it is absolutely essential to orient the filter correctly when placing it in the positioning equipment (in this case the syringe) so that this filter can be delivered at the desired time by presenting first its head 3, if the femoral access route has been chosen, or its legs 5, if the jugular route.
There are at present two principal positioning techniques, with and without prepackaging of the prosthesis to be introduced.
In the first case, the practitioner orients the prosthesis manually at the time of its introduction into the positioning equipment. A human error is therefore always possible. Moreover, the prosthesis risks being damaged during its handling.
When the filter is prepackaged, it is thus contained in a syringe whose free end (opposite that end bearing the plunger rod) is designed to be connected to the positioning equipment, such as a catheter, through which the prosthesis will move as far as the site of the chosen blood vessel where it will then be released.
In this case, the surgeon must necessarily choose the method of access to the patient prior to the operation, and he cannot then change this method. However, the surgeon may be forced to reconsider his choice on account, in particular, of the tortuous nature of vessels or the like.
With this system, he can change from one access route to the other only by once again fitting on the endpiece of the catheter a new prepackaged assembly comprising a new complete syringe enclosing a new prosthesis placed in the direction corresponding to the access route now chosen. This therefore makes it necessary to have at one's disposal a double supply of prepackaged syringes. In addition, the loss of time involved in replacing a complete syringe with another one increases the operating risks.
Other solutions derived from the latter have also been proposed. However, the systems envisaged have proven difficult to implement in practice, particularly on account of the packaging requirements imposed by most prostheses, and especially by the percutaneous filters used most often.